G-protein coupled receptors (GPCRs) are proteins responsible for transducing a signal within a cell. GPCRs have usually seven transmembrane domains. Upon binding of a ligand to a portion or a fragment of a GPCR, a signal is transduced within the cell that results in a change in a biological or physiological property or behavior of the cell. GPCRs, along with G-proteins, effectors (intracellular enzymes and channels modulated by G-proteins) and beta-arrestins, are the components of a modular signaling system that connects the state of intra-cellular second messengers to extra-cellular inputs. GPCR genes and gene products can modulate various physiological processes and are potential causative agents of disease. The GPCRs seem to be of critical importance to both the central nervous system and peripheral physiological processes. The GPCR protein superfamily is represented in five families: Family I, receptors typified by rhodopsin and the beta2-adrenergic receptor and currently represented by over 200 unique members; Family II, the parathyroid hormone/calcitonin/secretin receptor family; Family III, the metabotropic glutamate receptor family; Family IV, the CAMP receptor family, important in the chemotaxis and development of D. discoideum; and Family V, the fungal mating pheromone receptor such as STE2. G proteins represent a family of heterotrimeric proteins composed of alpha, beta and gamma subunits, which bind guanine nucleotides. These proteins are usually linked to cell surface receptors (receptors containing seven transmembrane domains) for signal transduction. Indeed, following ligand binding to the GPCR, a conformational-change is transmitted to the G protein, which causes the alpha-subunit to exchange a bound GDP molecule for a GTP molecule and to dissociate from the beta-gamma-subunits. The GTP-bound form of the alpha, beta and gamma-subunits typically functions as an effector-modulating moiety, leading to the production of second messengers, such as cAMP (e.g. by activation of adenyl cyclase), diacylglycerol or inositol phosphates.
Known and uncharacterized GPCRs currently constitute major targets for drug action and development. There are ongoing efforts to identify new G protein coupled receptors which can be used to screen for new agonists and antagonists having potential prophylactic and therapeutical properties. More than 300 GPCRs have been cloned to date, excluding the family of olfactory receptors. Mechanistically, approximately 50-60% of all clinically relevant drugs act by modulating the functions of various GPCRs.
GPR1 (Sequence ID Nos: 1 (human polynucleotide sequence, FIG. 1); 2 (human amino acid sequence, FIG. 2); 3 (mouse polynucleotide sequence, FIG. 3); 4 (mouse amino acid sequence, FIG. 4); 5 (rat polynucleotide sequence, FIG. 5); 6 (rat amino acid sequence, FIG. 6); 7 (rhesus macaque polynucleotide sequence, FIG. 7); 8 (rhesus macaque amino acid sequence, FIG. 8); 9 (cynomolgus monkey polynucleotide sequence, FIG. 9), and 10 (cynomolgus monkey amino acid sequence, FIG. 10)) has been described as an orphan G protein coupled receptor. The gene encoding GPR1 was assigned to the 2q33.3 region of human chromosome 2. GPR1 was tested in fusion assays for potential co-receptor activity by a range of HIV-1, HIV-2 and SIV viral strains (Farzan et al., J. Exp. Med., 186: 405-411, 1997; Shimizu et al., J. Virol., 73: 5231-5239, 1999; Shimizu et al., J. Gen. Virol., 89: 3126-3136, 2008; Shimizu et al., AIDS, 27: 761-769, 2009). Several HIV strains (GUN-1V, GUN-1/A, GUN-1/S, and GUN-1/T) efficiently used GPR1 as a co-receptor. This receptor therefore appears to be a co-receptor for immunodeficiency viruses that does not belong to the chemokine receptor family. Jinno-Oue et al. (J. Biol. Chem., 280: 30924-30934, 2005) have demonstrated that a synthetic peptide derived from the NH2-terminal extracellular region of GPR1 preferentially inhibits infraction of X4 HIV1.
Humanin (HN, Sequence ID No: 12 (human Humanin amino acid sequence, FIG. 12) is a recently identified peptide with a role in neuro-protection against Alzheimer's disease (AD) associated insults (Hashimoto et al., Proc. Natl. Acad. Sci. USA 98: 6336-6341, 2001). In fact, Humanin was first identified from cDNA library of surviving neurons from an AD patient. Since then, its protective role has been described not only from various AD related insults, but also against prion-induced (Sponne et al., Mol. Cell. Neurosci. 25: 95-102, 2004) and chemical-induced damage (Mamiya and Ukai, Br. J. Pharmacol. 134: 1597-1599, 2001), thus broadening its role as a neuroprotective factor. Subsequently it has been shown to be protective against many other cytotoxic agents (Kariya et al., Mol. Cell. Biochem., 254: 83-89, 2003) and to protect non-neuronal cells such as smooth muscle cells (Jung and Van Nostrand, J. Neurochem, 82: 266-272, 2003), rat pheochromocytoma cells (Kariya et al., Neuroreport, 13: 903-907, 2002) and lymphocytes (Kariya et al., Mol. Cell. Biochem., 254: 83-89, 2003). Structurally, HN is a 24 amino acid polypeptide that is transcribed from an open reading frame within the mitochondrial 16S ribosomal RNA in mammals (Hashimoto et al., Proc. Natl. Acad. Sci. USA, 98: 6336-6341, 2001). HN is both an intracellular and secreted protein. It has been detected in normal mouse testis and colon (by immunoblot and immunohistochemical analyses using specific antibodies against HN peptide) (Tajima et al., Neurosci. Lett., 324: 227-231, 2002). So far, little has been discovered about the regulation of its production. HN promotes cell survival by binding to a variety of pro-apoptotic protein partners, such as Bax-related proteins (Guo et al., Nature, 22: 456-461, 2003), IGF binding protein-3 (IGFBP-3) (Ikonen et al., Proc. Natl. Acad. Sci. USA, 100; 13042-13047, 2003), a cytokine complex involving CNTF receptor alpha/WSX-1/gp130 (Hashimoto et al., Mol. Biol. Cell., 20: 2864-2873, 2009), but also binds and activates with high affinity and potency the G Protein coupled receptors FPRL1 (alias FPR2) and FPRL2 (alias FPR3) (Ying et al., J. Immunol., 172: 7078-7085, 2004; Harada et al., Biochem. Biophys. Res. Comm., 324: 255-261, 2004).
Methods of identifying modifiers of GPR1 activity using Chemerin or Chemerin derivatives as ligands have been described in WO 2007/149807.